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It’s A Chemical World!

About one aspect of chemicals, there is no debate. They can trigger debate.

It’s a chemical world out there! We are awash in some fifty million known chemicals, the majority of which are created by nature, a minority by chemists. They’re not good or bad, not safe or dangerous. It all depends on how they are used, and what our exposure is. There is much debate about the effect of some chemicals on our lives, but about one issue there should be no debate. Chemicals are interesting! So, here’s a little quiz. Where would you encounter each of the following: para-dichlorobenzene, piperine, acetone peroxide.

If you’ve ever battled moths or nasty household smells, you’ve probably met para-dichlorobenzene. A registered insecticide, it does away with moths very nicely. It can also do away with smells in urinals either by masking the odour with its own strong smell or by preventing bacteria in stagnant urine from forming ammonia and other malodorous amines. That’s why it is a common ingredient in those urinal cakes that make for such inviting tinkle targets. You’ll also find para dichlorobenzene in various air fresheners. And since we breathe the air, you’ll find it in your blood. And what is it doing there? Probably not much good.

Para-dichlorobenzene is a known animal carcinogen and a suspected human one as well. Based on some elegant work using a tiny worm known as C. elegans, the suspicion is that this compound, as well as its chemical cousin naphthalene, can cause cancer by blocking apoptosis, a programmed process of “cell suicide” that occurs in all living organisms. Apoptosis is sort of a brake to prevent unchecked cellular proliferation, as happens in cancer. I wouldn’t worry about peeing on a urinal cake, but I’d rather not make a habit of sniffing para-dichlorobenzene elsewhere.

Now on to piperine, the compound responsible for the flavor of black pepper, the most widely used spice in the world. First cultivated in India some four thousand years ago, pepper became a much sought after commodity because of its ability to counter the offensive odours and tastes that were common before effective food preservation techniques were introduced. In the 16th century pepper was so valuable that dock workers in England were prohibited from wearing clothes with pockets or cuffs for fear that they would abscond with a few corns.

America’s first millionaire, Elias Derby of Salem, made his fortune by importing peppercorns and then used the money to endow Yale University. And now it is from Yale that we get a report of piperine’s potential role in breast cancer prevention. A combination of piperine and curcumin, a compound isolated from turmeric, when applied to cultured breast cancer cells in the lab, had the effect of decreasing the number of stem cells. Limiting stem cells limits the number of cells that have a potential to form tumours. Of course, such laboratory research rarely translates into effective practice when it comes to people, but the concept that cancer risk can be reduced with dietary compounds that have very low toxicity is an appealing one.

Hopefully acetone peroxide is a chemical you won’t encounter. It’s an explosive, and a powerful one at that. It was used in the infamous London bombings in 1907 and was also the substance that Richard Reid, the “shoe bomber,” was trying to ignite to trigger an explosion that could have brought down an American Airlines flight in 2001. Luckily Reid had been trudging around in rainy weather and the fuse in his shoe failed to ignite. He won’t be getting another chance to experiment with explosives, seeing that he is spending the rest of his life in jail. But you can thank Reid for having to remove your shoes when going through airport security.

Unfortunately, acetone peroxide is not difficult to make, requiring only acetone, hydrogen peroxide, a strong acid and a modicum of chemical knowledge. A highly unstable compound, it readily decomposes with heat or impact into acetone vapour and ozone. Hundreds of liters of gas can be produced from a few hundred grams of solid material in a fraction of a second! The shock wave created by this rapid release of gases is what we term an “explosion.” Unlike most explosives, acetone peroxide contains no nitrogen, making it “transparent” to airport detection equipment that tests for nitrogen-based residues. No wonder that acetone peroxide has earned the nickname “Mother of Satan.” Didn’t I tell you that chemicals are interesting?


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